Jad. Lair is an area below the habitat. Entrance is north and aross the top of the waterfall near the people there. They're not directly related tbh. You can train Firemaking/Woodcutting/Combat+Slayer in the Lair. Fletching too, but no-one does that cos its stupid.
You can spend 'favour' at the lair, which is gained by doing things in it, for herblore habitat seeds. The seeds you will get however, are dependant on what the jadinko's above would drop.